1. Field of the Invention
The invention relates generally to measurement, communication, and performance-monitoring equipment used in the installation and operation of geothermal well power systems of the kind for generating electrical power by utilizing energy from subterranean geothermal sources and, more particularly, relates to improvements in such arrangements for monitoring the operation of down-well geothermal power systems including efficient super-heated working fluid generation and hot brine pumping equipment for deep hot water wells for the beneficial transfer of thermal energy to the earth's surface.
2. Description of the Prior Art
The present invention is designed for use in the operation of geothermal well power generation systems of the general class disclosed in several prior United States patents issued to Sperry Rand Corporation:
H. b. matthews U.S. Pat. No. 3,824,973 issued Oct. 24, 1972 for a "Geothermal System and Method", PA0 H. b. matthews U.S. Pat. No. 3,898,020 issued May 8, 1974 for a "Geothermal System and Method", PA0 K. e. nichols et al. U.S. Pat. No. 3,905,196 issued Sept. 16, 1975 for a "Geothermal Energy Pump Thrust Balance Apparatus", PA0 J. l. lobach U.S. Pat. No. 3,908,380 issued Sept. 30, 1975 for a "Geothermal Energy Turbine and Well System", and PA0 H. b. matthews et al. U.S. Pat. No. 3,910,050 issued Oct. 7, 1975 for a "Geothermal Energy System and Control Apparatus".
The patents disclose geothermal energy recovery systems making use of energy stored by subterranean heat sources in solute-bearing water to generate a super-heated working fluid from a surface-injected flow of clean liquid; the super-heated working fluid then operates a turbine-driven pump within the well for pumping the hot brine at high pressure and always in liquid state to the earth's surface, where it transfers its heat in a binary closed-loop heat exchanger, vapor turbine, alternator combination for generation of electrical power. Residual brine is pumped back into the earth, while clean, cooled fluid is regenerated at the surface-located system and is returned to the deep well pumping system for generating the super-heated fluid.
The invention may readily be employed also in an alternative geothermal energy recovery system disclosed in the H. B. Matthews U.S. patent application Ser. No. 674,243 filed Apr. 6, 1976 for a "Geothermal Energy Conversion System", that makes use of thermal energy in solute-bearing well water during the period that it is pumped upward to the earth's surface through an extended heat exchanger for continuously heating a downward-flowing working fluid. The added energy of the latter fluid is then used within the well for operating a turbine-driven pump for pumping the hot well water at high pressure and always in liquid state to the earth's surface, where it is reinjected into the earth by a sump well. The temperature difference between the upward flowing brine and the downward-flowing working fluid is maintained in a predetermined manner along the length of the subterranean extended heat exchange element. After driving the deep well turbine-driven pump, the working fluid in supercritical state arises to the earth's surface in a thermally insulated conduit; at the earth's surface, electrical power generation equipment is driven by the ascending working fluid, after which it is returned into the well for reheating as it travels downward in the extended heat exchanger.
Such geothermal wells may be logged with a minor degree of success by methods previously applied in the oil well industry. In such tests, a canister which may contain sensors, a battery, and a recorder is lowered into the well and is then brought back to the earth's surface where the recorded data is retrieved. Such a time-consuming method is undesirable even in the oil well application, as it is not a real time method and requires removal of pumping equipment from the well. When a geothermal well pumping system is present in the well, its removal unless disabled cannot be considered on economic grounds and therefore only secondary ways of finding out what is occurring at the deep well pump site are actually available in the prior art. For example, the control system of the aforementioned Matthews et al. U.S. Pat. No. 3,910,050 provides the additional opportunity of display at the surface of certain secondary data about the over-all operation of the system, but direct measurements of primary parameters that instantaneously reflect information about the efficiency of operation of the deep well geothermal pump system are not provided. These latter are the primary parameters that are of major interest during installation, adjustment, and continued operation of geothermal systems.
In the H. B. Matthews U.S. Pat. No. 3,988,896, issued Nov. 2, 1976 for a "Geothermal Energy Pump and Monitor System", there is described a permanent and direct monitoring system, with respect to which the present invention is an improvement, desirably providing continuous monitoring of primary parameters by sensors located at the deep well pump itself. Permanently active sensors are employed for detecting fluid pressure and temperature changes too small and too slowly varying to be detected accurately by secondary means, but nevertheless significant with respect to the life and efficiency of the pump installation.
In U.S. Pat. No. 3,988,896, it is indicated that the parameters of primary interest include water pressure and temperature immediately below the pump, the pressure increment across the pump, and the rotational speed of the pump, each in the form of an electrical signal, these signals being communicated to a receiver and utilization means at the earth's surface. A pump-driven electrical generator supplies an alternating electrical signal whose frequency is representative of pump rotation speed, also supplying electrical energy required for multiplexing and for communication to the surface of the multiplexed signals.